PETALING JAYA - 1Malaysia Development Berhad must show proof of its investments and payments, said Tun Dr Mahathir Mohamad.
The former prime minister said the company's inability to do so would only lead to the assumption that the money it borrowed is lost.
Dr Mahathir said that to date, the company had only showed documents for the acquisition of power plants and the purchase of government land in Kuala Lumpur and private land in Penang.
"1MDB and the Prime Minister have not shown proof of the existence of the money from Cayman Islands.
"Is it in Singapore or has the US$1bil (S$1.3bil) disappeared? Statements without documentary proof are, as we have seen, quite useless. We need proof of all the investments and payments made by the 1MDB.
"Until signed documentary proof and not just statements by the chief executive officer or Prime Minister are shown, we have to assume that the money borrowed by 1MDB has disappeared," Dr Mahathir said in his latest posting in his blog chedet.cc.
The US$1bil (RM3.7bil) in question is one of the two tranches reportedly brought from Cayman Island to Singapore and deposited in the Swiss Bank.
Dr Mahathir said the money should have been brought back to Malaysia and the reasons given that Bank Negara would ask "too many questions" were not an excuse.
"According to the law, Bank Negara must get the approval of the (finance) minister to approve or disapprove any transaction. And the minister (Datuk Seri Najib Tun Razak) is the effective head of 1MDB. So what is so difficult about getting Bank Negara's approval?" he asked.